1. Field of the Invention
The present invention relates to a cooking oven, and in particular to a cooking appliance incorporating a single or dual oven cavity oven with a flexible heating system.
2. Description of the Related Art
It is well known that energy saving is an imperative for all the devices which consume energy and therefore contribute to environment pollution and/or greenhouse effect. This applies to domestic appliances, and particularly to domestic appliances using high level of energy like electric cooking ovens.
In the past, there have been attempts to improve oven efficiency and flexibility by providing removable partitions for oven cavities such that the oven may operate in a single cavity or a dual cavity configuration. U.S. Pat. No. 5,618,458 discloses an oven cavity into which food to be cooked can be placed, and a partition received within the cavity to divide the cavity into a plurality of cooking spaces. U.S. Pat. No. 4,780,597 discloses an oven with insertable partitions wherein the partitions carry heating elements.
It is an object of the present invention to provide an oven with a cavity that. improves oven performance (efficiency and effectiveness), provides greater flexibility in use, improved quality of cooking and better cleanability by means of a flexible heating system.
According to the invention, the oven comprises heating elements placed vertically on side walls of the cavity, in lieu of or in addition to traditional heating elements placed horizontally on top, bottom and rear walls. The concept is applicable to pyrolitic and non-pyrolitic ovens, and includes also the solution according to which the oven cavity does not have the traditional heating elements placed horizontally on top and/or bottom walls and/or the solution according to which the oven cavity is provided, on its back wall, with a traditional central forced air fan and a tubular heater or quartz lamp.
The use of the separating and insulating plate and of the heating elements according to the invention allows improved energy efficiency due to flexibility in use and optimization of heat transfer. Moreover it reduces cooking cycle times (effectiveness) due to smaller cavity and improved energy efficiency. The oven cavities of the oven according to the present invention can be run in static and convective modes singularly or separately. This increases flexibility in use. The reduced dimension of the sub-cavities and/or the use of heating elements placed on side walls of the cavity improve temperature uniformity in the cavity.
According to a first embodiment of the invention, four heating elements, two for each side of the oven cavity, are housed in suitable metal casings or xe2x80x98pocketsxe2x80x99 that are attached to the internal face of the cavity wall.
According to a second embodiment of the invention, four tubular heating elements, two for each side of the oven cavity, are housed in suitable metal casings or xe2x80x98pocketsxe2x80x99 that are attached to the external face of the cavity wall.
According to a third embodiment of the invention, four radiant heating elements are mounted directly behind the walls of the oven cavity. In such embodiment the oven cavity can be provided with openings closed by glass ceramic plates or metal plates that cover the heater elements.
According to a fourth embodiment of the invention, a twin radiant heating element is mounted behind the metal side wall or behind a metallic or glass ceramic plate and is located at the center of each side wall of the oven. In this case the heaters are aligned so as to transfer heat also to the faces of the separating and insulating plate, underneath the food tray or container as well as to the cavity. The scope here is to improve baking performance especially in terms of browning, crisping etc. through the use of appropriate reflection.
According to a fifth embodiment of the invention, four radiant heating elements in the form of quartz lamps, two for each side of the oven cavity are used. These are housed in suitable metal reflectors that are attached to the external face of the cavity wall and covered either by a metal plate (which can be integral with the oven wall) or by ceramic glass.
According to a sixth embodiment of the present invention, the oven comprises a forced air fan and a heater for the main cavity and upper sub-cavity and two quartz lamps for the lower sub-cavity only. The heater can be a circular tubular heater or a quartz lamp.
According to an seventh embodiment of the invention, the inclusion of a rotating table on the separating plate improves browning, crisping, heat distribution and hence improves efficiency (time and energy saving) and effectiveness (cooking results).
The walls of the oven cavity, of the oven door or accessories thereof (e.g. baking tray) are preferably coated with coatings including fluoropolymers with or without PTFE additives and fillers, Sol-Gel generated films and PECVD (Plasma Enhanced Chemical Vapor Deposition) generated films. All the above coatings have the specific intent to create an abrasive-corrosive resistant and non-stick surface applied to metallic (e.g.. stainless steel) or non metallic (e.g. enamel) substrate. These coatings can be applied to all or part of the cavity or oven accessories or parts e.g. baking trays, oven door, racks etc. The coatings can be applied to sheet, pre-formed sheet or ready-to-use parts.
The separating and insulating plate may be made of a material different from metal, i.e. polymeric material (preferably silicone resin type), tempered glass and Pyrex(trademark) glass. The separating and insulating plate may also include a series of indications and/or guides (e.g. pressed/molded directly in the plate material) to help the consumer position the food tray or container correctly. Further indications such as xe2x80x9cDanger hot surfacexe2x80x9d or xe2x80x9cDanger heavy weightxe2x80x9d can also be added.
When installed, the separating plate sits on side supports that also act as heat and odor barriers around the perimeter of the cavity.
When tempered or Pyrex(trademark) type glass is used for the separating plate, visibility inside the cavity is greatly improved, although in this case thermal insulation is reduced. In order to improve thermal insulation, the glass separating plate may have an interspace in which vacuum is created. Visibility is further improved by using low voltage (24 V) or high (220 V) voltage, low (10-50 W) wattage, halogen illumination devices in both sub-cavities. These can be positioned on any of the cavity walls although the preferred position is either at the rear of the cavity or on the side walls.
High temperature silicone resin plastic may also be used to realise all or part of the separator; in this particular case the plastic must be suitable up to 500xc2x0 C. continuous use i.e. also for pyrolitic ovens.